The present invention relates to an intravascular imaging device and methods for use and manufacture thereof, and more specifically to an imaging guidewire which can be used to receive a therapeutic catheter having a guide lumen to direct the catheter to a desired position within a vessel of a body.
Intraluminal, intracavity, intravascular, and intracardiac treatment and diagnosis of medical conditions utilizing minimally invasive procedures is an effective tool in many areas of medical practice. These procedures are typically performed using imaging and treatment catheters which are inserted percutaneously into the body and into an accessible vessel of the vascular system at a site remote from the vessel or organ to be diagnosed and/or treated, such as the femoral artery. The catheter is then advanced through the vessels of the vascular system to the region of the body to be treated. The catheter may be equipped with an imaging device, typically an ultrasound imaging device, which is used to locate and diagnose a diseased portion of the body, such as a stenosed region of an artery. The catheter may also be provided with a therapeutic device, such as those used for performing interventional techniques including balloon angioplasty, laser ablation, atherectomy and the like. Catheters are also commonly used for the placement of grafts, stents, stent-grafts, etc. for opening up and/or preventing closure of diseased or damaged vessels.
Catheters having ultrasound imaging and/or therapeutic capabilities are generally known. For example, U.S. Pat. No. 5,313,949, issued to Yock, the disclosure of which is incorporated herein by reference, describes an intravascular ultrasound imaging catheter having an atherectomy cutting device. Generally speaking, there are two predominant techniques used to position the therapeutic catheter at the region of interest within the body. The first technique simply involves directly inserting the catheter into a vessel and advancing the catheter through the branches of the vascular system by pushing and steering the catheter to enter a desired branch as the catheter is moved forward. The use of this technique typically requires that the catheter be equipped with an extremely flexible guidewire at its distal tip which can be aimed in different directions by rotating the catheter or by actuating a steering mechanism.
The second technique utilizes a separate guidewire which is first positioned within the vascular system such that a distal end of the guidewire extends beyond the region of interest. The guidewire is routed into position by inserting it into a vessel and advancing it through the vascular system by pushing and steering the guidewire similar to the method previously described for a catheter. The catheter being inserted includes a guidewire lumen which is sized to receive the guidewire. The guidewire lumen may extend the entire length of the catheter, or alternatively, the guidewire lumen may be a short length lumen disposed at the distal end of the catheter. Once the guidewire is in place, the therapeutic and/or imaging catheter is routed over the guidewire to the region of interest while holding the guidewire fixed in place.
The use of a guidewire provides several advantages. Routing a catheter or guidewire through a circuitous path of the complex network of blood vessels to a region of interest can be a tedious and time consuming task. Placement of the guidewire is made even more difficult with increasing vessel occlusion which may occur in the later stages of vascular disease. In addition, many catheter procedures require the use of several different catheters. For instance, an imaging catheter may be initially inserted to precisely locate and diagnose a diseased region. Then, the imaging catheter may be removed and a therapeutic catheter, such as an balloon angioplasty catheter, may be inserted. Additional therapeutic or imaging catheters may be employed as necessary. Accordingly the successive insertion and removal of each of these catheters, called catheter xe2x80x9cexchanges,xe2x80x9d is required because there is only enough space within the vessels to rout a single catheter at a time. Hence, with the use of a guidewire, the tedious and time consuming task of routing a device to the region of interest need only be done once. Then, the much easier procedure of routing catheters over the guidewire to the region of interest may be performed as many times as the desired therapy dictates.
In order to locate the site of interest and facilitate proper placement of the guidewire, and further to observe the site during and after treatment, a guidewire may include an imaging device, commonly a rotating ultrasonic imaging transducer or a phased-array ultrasound transducer. Providing the guidewire with imaging capability may eliminate the need for insertion of an imaging catheter or imaging capabilities in the therapeutic catheters. Hence, an imaging guidewire can reduce the number of catheter exchanges that a physician must do during a surgical procedure.
Imaging guidewires have been disclosed generally, for example, in U.S. Pat. No. 5,095,911, issued to Pomeranz, the disclosure of which is incorporated herein by reference. The imaging guidewire disclosed in Pomeranz includes an elongate, flexible body. A housing enclosing a rotating transducer is secured to the distal end of the body. A drive shaft extends through a lumen of the body and is coupled to the transducer. In order to image a different region of interest, the entire guidewire is moved back and forth to position the housing and transducer adjacent the region.
However, once the physician has carefully placed the imaging guidewire, it is preferable to maintain the guidewire in a fixed position so as not to lose the correct placement of the guidewire. At the same time, it is often desirable to obtain images along an axial length of diseased area. This currently requires axial translation of the imaging device by axially translating the entire guidewire. The problem with advancing and pulling back the imaging guidewire is that the correct placement of the guidewire may be lost and the physician must then spend more time repositioning the guidewire.
Furthermore, there are significant technical obstacles in producing an imaging guidewire having a sufficiently small diameter to fit within a guidewire lumen of a catheter while at the same time exhibiting the necessary mechanical and electrical characteristics required for placement in the vascular system and generation of high quality images. For instance, on typical catheters sized to be inserted in the smaller coronary vessels, the guidewire lumen is sized to receive a guidewire having a maximum diameter of 0.035xe2x80x3. In addition, the 0.035xe2x80x3 guidewire must have sufficient flexibility to traverse a tortous path through the vascular system, and also have sufficient column strength, or pushability, to transmit a pushing force from a remote proximal end of the guidewire, along a winding path, to the distal end thereof.
Moreover, if a rotating transducer is utilized, the drive shaft extending to the transducer must have stable torsional transmittance in order to achieve high quality images. Hence, the drive shaft must not only be flexible, but also must be torsionally stiff to limit angular deflection and nonuniform angular velocity which can cause image distortion. The drive shaft must also be mechanically and electrically connectable to a motor drive and transducer signal processing electronics. The connection must be easily disconnectable so that a guidewire lumen of a catheter may be threaded over the proximal end of the guidewire. This requirement also limits the size of the connector on the drive shaft because the connector must also fit through the guidewire lumen. The drive shaft and connector must also provide a high quality transmission of imaging signals between the imaging device and the signal processing equipment.
Therefore, a need exists for an improved imaging guidewire which overcomes the aforementioned obstacles and deficiencies of currently available guidewires.
The present invention provides an intravascular guidewire, and methods of use and manufacture, which can accomplish longitudinal translation of an imaging plane allowing imaging of an axial length of a region of interest without moving the guidewire thereby maintaining proper positioning of the guidewire to effectively facilitate the introduction of catheters over the guidewire to the proper position. Accordingly, the imaging guidewire of the present invention comprises a body in the form of a flexible, elongate tubular member. An elongate, flexible imaging core is slidably and rotatably received within the body.
The imaging core includes a rotatable drive shaft having an imaging device mounted on its distal end. The imaging device produces an imaging signal which can be processed by signal processing equipment to create an image of the feature at which the imaging device is directed. An electrical cable runs through the center of the drive shaft extending from the imaging device at the distal end to a connector attached to the proximal end of the drive shaft. The connector detachably connects the driveshaft to a drive unit and electrically connects the electrical cable to imaging signal processing equipment. At least a distal portion of the body through which the imaging device images is transparent to imaging signals received by the imaging device. The transparent portion of the body extends for at least an axial length over which imaging will typically be desirable.
The body and the imaging core are cooperatively constructed to enable axial translation of the imaging core and imaging device relative to the body. This allows imaging along an axial length of a diseased region in the body without moving the body.
In the preferred method of using the imaging guidewire of the present invention, the imaging guidewire is first inserted percutaneously into a vessel of the vascular system, usually at a site remote from the site of interest within the body. The imaging guidewire is routed to the region of interest by advancing it through the branches of the vascular system by pushing and steering the guidewire as the guidewire is fed into the vessel. The imaging device may be activated during this process to aid in routing the guidewire and locating a diseased region of the body. The imaging guidewire is positioned such that the distal end extends beyond the diseased region with the transparent portion of the body approximately centered at the region of interest. Alternatively, a standard guidewire may first be inserted and routed to the region of interest. Then, a catheter having a full-length guidewire lumen is fully inserted over the standard guidewire. The standard guidewire is then removed and the imaging guidewire is inserted through the guidewire lumen to the desired position.
At this point, in order to image the length of the diseased region, the imaging device may be axially translated forward and back relative to the body which is preferably fixed in place.
Once the medical condition has been diagnosed and a treatment is chosen, a therapeutic catheter having a guidewire lumen, or a series of therapeutic catheters, may be routed over the guidewire to the diseased region to perform the desired treatment. The imaging device on the guidewire may further be used to monitor the treatment while it is being performed and/or to observe the treated area after the treatment is completed. Alternatively, if the imaging device cannot image through the therapeutic catheter, the catheter may be pulled back to expose the imaging device.
Accordingly, it is an object of the present invention to provide an improved imaging guidewire and method of using the same.
A further object of the present invention is to provide an improved imaging guidewire which can image along an axial length of a region of interest while maintaining a fixed guidewire position.